Because gammadelta (gd) T cells populate epithelial surfaces, respond rapidly to infectious challenges, and are stimulated by nonpeptide antigens without classic MHC restriction, they may have important and unique applications for vaccine development. A direct role for gd T cells in vaccine immunity was suggested by our studies in humans vaccinated with either the live attenuated TB vaccine, bacilli Calmette-Guerin (BCG), or live canarypox vectored AIDS vaccines. We found that BCG and canarypox vaccination induced memory-like gd T cells characterized by more rapid and potent secondary responses. The major focus of this proposal is to determine whether gd T cells induced by these live vaccines provide important helper and/or effector functions for protective immunity. We will test 3 hypotheses: 1) Stable, antigen specific gd T cell lines and alphabeta (ab) T cell clones can be generated from BCG vaccinated, canarypox vaccinated, latently Mtb infected and HIV infected individuals; 2) Human gd T cells induced by BCG and canarypox vaccinations can provide helper functions for the generation and/or recall of optimal memory immune ab T cell responses; and 3) Human gd T cells will provide direct or cooperative immune effector functions able to inhibit replication of intracellular pathogens. Gd T cell lines will be expanded with mycobacterial, canarypox and HIV antigens. Autologous CD4 and CD8+ ab T cell clones will be generated specific for Mtb Ag85B and HIV supermotif epitopes relevant for the development of vaccines potentially useful in genetically diverse populations. The helper (or inhibitory) effects of gd T cells on cytokine and cytolytic effector functions mediated by ab T cell clones will be studied. In addition, we will investigate the ability of gd T cells to facilitate (or inhibit) primary induction of naive and/or secondary reactivation of memory polyclonal ab T cells, using mycobacteria and HIV infected dendritic cells as APC. Finally, the involvement of gd T cells in protective effector mechanisms capable of inhibiting intracellular replication of mycobacteria inside macrophages and HIV inside T cells will be examined.